The present invention relates to a platen of an injection molding machine. The present invention further relates to a two-platen injection machine equipped with such a platen.
U.S. Pat. No. 5,593,711 discloses a platen for use in a plastics injection molding machine, with the platen including a base plate, a frustoconical center part, and a front plate in parallel relationship to the base plate for carrying a molding tool. The base plate has corners formed with bores for receiving tie bars. The center part is hollow and has a base disposed at a central location of the base plate, with the front plate situated upon the truncated top of the center portion. The front plate is thus supported solely in midsection by the center part. In this way, the front plate is presumed to remain planar, when a clamping force is applied so as to prevent an opening of the half-molds of the molding tool.
European Pat. No. EP 0 789 648 B1 discloses an injection molding machine with a generally C-shaped machine frame with two frame limbs in the absence of interconnecting tie bars. Supported by one limb is a fixed platen, while the other limb has mounted thereto a flange plate of a clamping unit. The clamping unit includes a hydraulic piston and cylinder unit to displace the moving platen, supported by the machine frame. The flange plate and the fixed platen are secured via so-called holding elements to the limbs of the machine frame. During closing operation, the holding elements of the flange plate are exposed to a tensile load while the fixed platen is loaded by a compressive force. The holding elements resemble the operation of springs whose elasticity is smaller than that of the machine frame. The holding elements are distributed over the vertical dimension of the fixed platen and the flange plate and exhibit different elasticity, whereby the lower holding elements have a greater elasticity than the upper holding portions. The holding portions are made of spring steel and are formed with slots for effecting material weakenings. The lower portion includes hereby several or deep slots to enhance the elasticity. When pushing the frame limbs of the machine frame apart at the top during the injection operation, the fixed platen and the flange plate can undergo a tilting movement relative to the machine frame to thereby maintain parallelism of the platens. The holding elements thus form an axis-less hinge which besides the rotary movement also permit a translatory movement.
European Pat. No. EP 0 381 107 B1 discloses a clamping unit for a horizontal two-platen injection molding machine for plastics. The injection molding machine includes a fixed platen and a moving platen for carrying confronting half-molds. The fixed platen has a rectangular shape and is connected with the moving platen by spindles arranged at the four corners or an imaginary tetragon. The spindles are hereby arranged non-rotatably and cantilevered on the fixed platen. The moving platen is displaceable in the direction of the fixed platen along the spindles at the corners for opening and closing the half-molds. Mounted on each spindle on a side of the moving platen distal to the half-mold is a spindle nut for operation of the moving platen. The spindle nuts are rotated together by an electric motor and configured as a ball screw nut. After closing the half-molds, a clamping force is applied upon the half-molds by a hydraulic piston and cylinder unit which act on the spindles and spindle nuts and include an annular piston through which the respective spindle is guided. To prevent opening of the half-molds after injection operation, the piston and cylinder unit is double-acting. A tilting or deformation of the platens during application of the clamping force is accompanied by a bending of the spindles which are thus subject to increased wear, ultimately resulting in their destruction.
It would therefore be desirable and advantageous to provide an improved platen and improved two-platen injection molding machine to obviate prior art shortcomings and to be of simple construction and yet enabling an elastic securement for a connection of the platen to a holding and/or guiding element.